The present invention relates to a motor-driven compressor including an injection port that delivers intermediate pressure refrigerant to a compression chamber.
Generally, an injection pipe, which forms a portion of an external refrigerant circuit, is connected to an injection port. A gas-liquid separator is connected to the injection pipe. A check valve is arranged in the injection pipe. The check valve opens the injection pipe during a high-load operation, such as when a warming operation is performed in a refrigeration cycle, and closes the injection pipe during a low-load operation, such as when a cooling operation is performed. During a high-load operation in the refrigeration cycle, the gas-liquid separator separates refrigerant into liquid refrigerant and gas refrigerant, which has an intermediate pressure. The intermediate pressure gas refrigerant is delivered to a compression chamber through the injection pipe and the injection port. This increases the amount of gas refrigerant that flows into the compression chamber and improves the performance of the motor-driven compression during a high-load operation in the refrigeration cycle.
To further improve the performance of the motor-driven compressor during a high-load operation in the refrigeration cycle, the injection port may be enlarged to increase the amount of gas refrigerant that flows into the compression chamber. However, if the motor-driven compressor is, for example, of a scroll type, an enlarged injection port would connect adjacent compression chambers as the orbiting motion of the movable scroll moves the spiral wall of the movable scroll to a location overlapped with the injection port. In such a case, refrigerant would leak from the compression chamber having a high pressure to the compression chamber having a lower pressure. This would lower the performance of the motor-driven compressor.
Thus, there is usually more than one injection port so that adjacent compression chambers are not connected through the same injection port when the spiral wall of the movable scroll moves. In comparison to when there is only one injection port, the employment of a plurality of injection ports increases the amount of gas refrigerant that flows into the compression chambers and further improves the performance of the motor-driven compressor during a high-load operation in the refrigeration cycle.
Further, the end of the injection port connected to the injection pipe includes a valve mechanism so that the refrigerant flowing from the compression chamber to the injection port does not reversely flow into the injection pipe. Japanese Laid-Open Patent Publication No. 8-303361 describes a prior art example of a valve mechanism. The valve mechanism includes a spool valve and a coil spring, which biases the spool valve to a valve close position and disconnects the injection port and the injection pipe.
When the pressure of the intermediate pressure gas refrigerant from the injection pipe acts on the spool valve, the spool valve moves to a valve open position against the biasing force of the coil spring and connects the injection port and the injection pipe. This delivers gas refrigerant to the compression chamber through the injection pipe and the injection port. When the pressure of the intermediate pressure gas refrigerant from the injection pipe no longer acts on the spool valve, the biasing force of the coil spring returns the spool valve to the valve close position. This restricts a reversed flow of the refrigerant from the compression chamber to the injection pipe via the injection port.
The spool valve reciprocates between the valve open position and the valve close position in accordance with the relationship of the biasing force of the coil spring and the pressure of the intermediate pressure gas refrigerant from the injection pipe. Thus, the response of the spool valve is slow. This may hinder smooth delivery of the gas refrigerant to the compression chamber from the injection pipe and the injection port. In this case, refrigerant may reversely flow from the compression chamber to the injection pipe through the injection port. Thus, it is difficult to improve the performance of the motor-driven compressor during a high-load operation in the refrigeration cycle.
Japanese Laid-Open Patent Publication No. 11-107945 describes another prior art example of a valve mechanism. The valve mechanism includes a reed valve and a retainer formation plate, which includes a retainer that restricts the open degree of the lead valve. The reed valve opens when the intermediate pressure refrigerant gas from the injection pipe acts on the reed valve. When the reed valve opens, contact with the retainer restricts the open degree of the reed valve. As the reed valve opens, gas refrigerant is delivered to the compression chamber from the injection pipe and the injection port. The reed valve closes when the pressure of the intermediate pressure gas refrigerant no longer acts on the reed valve. This restricts a reversed flow of the refrigerant from the compression chamber to the injection pipe via the injection port.
In comparison with the spool valve, which is configured to reciprocate between the valve open position and the valve close position in accordance with the relationship of the biasing force of the coil spring and the pressure of the intermediate pressure gas refrigerant from the injection pipe, the reed valve has a quicker response. Further, the reed valve allows the performance of the motor-driven compressor to be satisfactory during a high-load operation in the refrigeration cycle.